Alright guys i searched this up on google and found multiple answers but i still do not get it. I was driving my aunts car and it was automatic with P R N D4 D3 (i think it had one more but i forgot) i asked her which one to use she said d4 i said why she said idk just use that one. I said ok so that got me wondering what the difference was.

Heres what i got from google. Some said D3 was overdrive and to use it while going up hills or down hills and that its good for driving in the city because you constantly stop and thats saves gas because it doesnt have to switch from 3rd to 4th gear like in D4.Others said d3 is just to be used in hills and that it burns more gas than d4. So can someone please thoroughly explain to me the difference.

I know a lot of time D4 is overdrive which is what you want for the best fuel consumption. D3 would take it out of overdrive, making it more responsive to throttle imput and it wouldn't have to be constantly downshifting when going up hills...

It means that car only has 4 gears. If you put it in D3 then the transmission will not shift higher than 3rd gear. This is used when going up hills and poo, to keep the RPMs higher so you can climb the hill.